1. Field of the Invention
The present invention relates to a magenta toner for developing electrostatic images used for electrophotography, electrostatic recording, electrostatic printing and other purposes, a resin, a colored molded resin member and a color filter dyed with a red dis-azo dye having the triphenylmethane structure.
2. Description of the Prior Art
In recent years, there have been increasing demands for color toners which offer images of various desired colors as necessary with the diversification of purpose of use of copying machines and printing machines, etc. So-called three primary color toners which offer yellow, magenta and cyan colors, respectively, are important in obtaining full-color images.
This kind of color toners basically comprise a toner resin and a coloring agent. To improve toner chargeability, a light-colored or colorless charge control agent providing a positive or negative charge is often added. When this toner is used as a two-component developing agent, the electrostatic latent image formed on a photoreceptor by charging and exposure is visualized by developing it with the toner charged together mixing with a carrier and transferring the resulting toner image onto transfer paper or another transferee.
To obtain a full-color image by superposing toner images of yellow, magenta and cyan colors, the three subtractive primaries, using such toners for color electrophotography etc., each toner is required to have a good spectral property and transparency for color reproduction. Transparency is also required in toners used for color electrophotography for overhead projectors (hereinafter referred to as OHP). It should also be noted that these toners are required not to be prone to discoloration, fading or bleeding due to light or heat.
Organic pigments are generally most often used as coloring agents for color toners. However, most organic pigments are unsuitable for imparting a color to toners to yield color toners which are required to be transparent in superposing development because they are incompatible with binder resin.
A number of means have been proposed to meet such requirements as far as possible. For example, Japanese Patent Unexamined Publication No. 295069/1987 discloses color toners incorporating various oil-soluble dyes or dispersion dyes; Japanese Patent Unexamined Publication No. 15555/1987 discloses a magenta toner incorporating a Rhodamine dye; Japanese Patent Unexamined Publication No. 217465/1989 discloses a magenta toner incorporating an anthraquinone dispersion dye.
However, color toners incorporating an oil-soluble dye or dispersion dye which is soluble in resin can cause copied image quality deterioration during long term repeated use, thus posing a problem to be solved.
To impart colors to thermoplastic resins, thermosetting resins, color filters, etc., various pigments and dyes are used according to respective uses and purposes.
For example, organic pigments are often used for this purpose, since they are excellent in color fastness to light and heat resistance and offer a wide variety of colors and a lot of brilliant colors.
Oil-soluble dyes and dispersion dyes are used to obtain transparent glossy products, since they possess excellent solubility in resin.
With respect to colored resins and colored molded resin members, transparency is often demanded as well as color fastness to light, bleeding resistance and resistance against heat during molding or in other situations.
Optical color filters needed for television cameras, liquid crystal televisions, flat panel displays on computers, etc., must be good in spectral property and transparency.
Examples of red dyes for optical filters include those disclosed in Japanese Patent Unexamined Publication No. 278569/1989.
Although color filters are often produced by dyeing a dyable film of gelatin, casein, polyvinyl alcohol or the like on a transparent resin or glass base plate with a dye having a given spectral property by printing, sublimational transfer, etc., it is desirable to color the resin itself from the viewpoint of durability.
Of such conventional coloring agents, organic pigments often fail to satisfy the requirement for transparency because they are almost insoluble in resin. On the other hand, oil-soluble dyes and dispersion dyes are prone to discoloration, fading, and bleeding.
Therefore, none of the colored resins, colored molded resin members and color filters which incorporate a conventional coloring agent are said to fully satisfy the essential requirements described above.